Distance measurement can be performed using the fact that the time of flight (TOF), which is the period from the transmission of an optical pulse to the reception of the pulse reflected on an object and returned, depends on the distance to the object. This distance measurement using the TOF method has a problem in which an error occurs in the distance measurement result due to the change of the measurement condition and measurement environment and hence the measurement accuracy reduces.
In Patent Literature 1, in order to suppress the reduction in measurement accuracy, a distance measurement value is calculated on the basis of the exposure amount obtained from each of two exposure pulses of different phases.